In the case of restraint, gas generators are to make compressed gas available as quickly as possible for example for unfolding a gas bag or actuating a belt tensioner. Therefore, in the case of restraint, the bursting disc closing the outflow opening should be destroyed as early as possible. Usually the bursting disc is destroyed by the pressure rise which is caused by the combustion of the propellant. However, the time from the releasing of the igniter up to the predetermined pressure being reached, which leads to the destruction of the bursting disc, is relatively long. Therefore, attempts were made in the past to shorten this time by special measures. For example, there are gas generators in which a separate igniter is provided which serves only for the destruction of the bursting disc, which, however, increases the expenditure for the gas generator.
EP 0 673 809 A1 provides for a gas generator which, in addition to a combustion chamber in which the igniter is also provided, has a pressure chamber, filled with compressed gas, and also has a mixing chamber. Adjoining the igniter is a so-called booster charge which is intended to intensify the ignition effect, and the propellant adjoins the booster. A pressure chamber, filled with gas, communicates with the combustion chamber. A mixing chamber, in turn, is in flow connection with the combustion chamber and the pressure chamber. After ignition of the propellant, a first increase in pressure occurs in the mixing chamber. The compressed gas which is also present in the mixing chamber reacts chemically with the hot gas produced by the combustion of the propellant, whereby the pressure in the mixing chamber exceeds the predetermined pressure necessary for the destruction of the bursting disc.
From the EP 0 554 919 B1 a further gas generator is known. The latter has a pressure chamber and a propellant charge chamber, which are not connected to each other in the non-activated state. The propellant charge chamber is closed off by the bursting disc. The squib itself directly adjoins the propellant charge having a heating charge, and is integrally connected thereto. Immediately upon igniting the squib, the propellant charge is ignited. The generated gas leads to an increase in pressure in the propellant charge chamber and to a destruction of the bursting disc.